On Feb. 1, a Turkish national named Ecevit Sanli walked up to the side entrance of the U.S. Embassy in Ankara like many others had done that day. Dressed inconspicuously, he waved a manila envelope at the man inside the guard booth as he approached the entrance. The security guard had no reason to distrust the man approaching the checkpoint; the entrance is used to screen packages, and perhaps the guard assumed Sanli was dropping off a document or was a visa applicant at the wrong entrance. What the guard did not know, perhaps, is that Sanli was a person of interest to the Turkish police, who suspected that he was plotting an attack.

The guard opened the door of the access control building -- the outermost door of the embassy compound -- to speak to Sanli, who took one step inside before detonating the explosive device that was strapped to his body. The explosion killed Sanli and the security guard, seriously wounded a journalist who was visiting the embassy and left two other local guards who were manning the entrance with minor injuries.

The embassy's local security personnel, as designed, bore the brunt of the attack. They are hired and trained to prevent threats from penetrating the embassy's perimeter. The low casualty count of the Feb. 1 attack is a testament to the training and professionalism of the local guards and the robust, layered security measures in place at the embassy -- factors for which those responsible for the attack apparently did not sufficiently plan.

Layers of Security

Sanli apparently had hoped to breach the outer perimeter of the compound and to detonate his device inside the embassy building. Reportedly he carried a firearm and a hand grenade, and the way he approached the access control point likewise suggests he hoped to gain entry. Had he wanted to kill Turkish citizens, he could have done so simply by hitting the visa line outside the embassy.

At embassy compounds, secondary access control posts for vehicles and pedestrians typically are staffed with fewer guards than more heavily traversed access points, such as the main entrance or the entrance to the consular section. This particular access point had two guards at the vehicular entrance and a third guard to receive and screen packages and pedestrians. Since there was no drop slot for packages and envelopes, the guard inside the access point had to open the exterior door to receive deliveries. It is likely that the plotters knew about this procedure, which probably factored into their decision to breach the perimeter at this entrance. Moreover, the attack happened around lunchtime, so it is also possible that attackers thought the guards would be inattentive.

Though these smaller access control points have fewer people guarding them, they still boast at least two heavy security doors that all visitors must pass through. Many embassy compounds, including the one in Ankara, have a third door located inside the building. This multiple-door configuration, referred to as a sally port by security officers, provides an additional level of security at perimeter security posts. Sally ports equipped with magnetic locks and reinforced doors can also serve as effective traps for intruders.

The access control point constitutes just the outer perimeter of the embassy. There is also another layer of external security at the entrance to the embassy building itself. It is possible that Sanli thought he could somehow use his weapon or grenade to penetrate that layer once he got through the access control center, but the forced entry/bullet resistant doors and windows on the embassy's exterior would not have been quickly or easily penetrated by such weapons.

Whatever his plan, Sanli never had the opportunity to fully execute it. He was stopped immediately inside the access control center by the security guard and detonated his suicide device just inside the door. The force of the blast blew the outer security door off its hinges and cracked the reinforced concrete exterior wall of the access control building. But the embassy perimeter was not breached, and Sanli never got near the embassy building.

Security Designs

Embassy security measures are designed with specific threats in mind. Sanli, for example, executed precisely the type of attack that embassy security was meant to counter: an isolated terrorist strike that circumvents a host country's police and security services. Ankara is an older embassy office building, but it has received security upgrades over the past few decades that have given the facility decent access control and concentric layers of security meant to stymie intrusions.

Like most older embassy buildings, however, it does not meet the security requirements put in place in the wake of the embassy bombings of the 1980s. The U.S. Consulate General building in Istanbul, which was completed in 2003, exemplifies a building that meets those requirements. Not only is it constructed to specifications, it is also appropriately far enough from the street to help counter threats, such as those posed by Sanli, and to help withstand the damage of a vehicle bomb.

Such was the case at the newly built and occupied U.S. Embassy in Tripoli, Libya, in May 2011. After U.S. diplomats were ordered to leave the country, the local security force was unable to prevent a large mob, which constituted security forces and Moammar Gadhafi supporters, from ransacking, looting and burning the facility. The attack rendered the building uninhabitable.

Embassy security measures are also not designed to prevent prolonged assaults by militant groups armed with heavy weapons. Security measures can only provide a delay against a persistent attack by a mob or militant organization. They cannot withstand an indefinite assault. Without extraordinary security like that of the U.S. Embassy in Beirut in the 1980s and 1990s, embassy security only works when the facility enjoys the support and protection of the host country as mandated by the Vienna Convention on Diplomatic Relations.

The Attackers' Weakness

Sanli's method of attack played right into the strength of the embassy's security measures. Perhaps he and his colleagues in the Revolutionary People's Liberation Party-Front believed Sanli could threaten or shoot his way through the embassy's concentric rings of physical security. If so, they underestimated the physical security measures in place and the dedication and bravery of the local guard force.

Notably, attack planning is not a strength of the Revolutionary People's Liberation Party-Front. Over the past decade, the group has conducted several attacks, including five suicide bombings, but their attacks have been famously poorly planned and executed. Often they fail to kill anyone but the suicide bomber. They also have had problems with the reliability of their improvised explosive devices, such as the suicide vest that failed to detonate during the suicide bombing attack against the Turkish justice minister in April 2009.

The Revolutionary People's Liberation Party-Front's Sept. 11, 2012, suicide bombing against a police station in Istanbul killed the bomber and one police officer. In that attack, the bomber threw a grenade at the security checkpoint at the building's entrance, but when the grenade failed to detonate he was unable to get past security at the building's entrance. Only then, in a move similar to the Feb. 1 attack, did he detonate his device.

Following Operation Desert Storm in 1991, Devrimci Sol, the Revolutionary People's Liberation Party-Front's parent organization, conducted a spate of attacks in Turkey that targeted the United States and NATO. Because of the timing, U.S. terrorism investigators believed that Saddam Hussein's government sponsored these attacks. Currently, some leaders of the Revolutionary People's Liberation Party-Front's factions live in Syria and maintain close connections with the al Assad regime. Some of the group's militants have fought with the regime forces, and the group has published statements supporting the al Assad regime. They have also fomented pro-al Assad and anti-intervention demonstrations inside Turkey. This pro-Syrian sentiment, or perhaps even financial enticement from the Syrian government itself, could explain the motive for the attack against the U.S. Embassy. Therefore, it is possible that there could be other anti-U.S. or anti-NATO attacks like those seen in 1991.

The Feb. 1 bombing serves as a timely reminder of several facts that tend to be overlooked. It reminds us of the underlying terrorist threat in Turkey. It also reminds us that not all suicide bombers are jihadists, let alone religious. Indeed, there is a long history of secular groups engaging in suicide terrorism. Last, it reminds us that not all threats emanate from al Qaeda and the constellation of groups and individual actors gathered around its ideological banner.

Perhaps most important, the incident highlights the heroism and dedication of the local guards who serve at U.S. embassies around the world. In the Feb. 1 attack, the embassy's security equipment functioned as designed, and the guards performed as they were trained, undoubtedly saving many lives. These local guards are often criticized when they make a mistake, but they are too frequently overlooked when security works